Minor fixes after #5537 (#5538)

* Restore '+' prefix when charging in the footer w/ letters prefixes

Regression since #5537

* Don't use a full battery icon in the menu entry

Make it clear that one isn't in-sync with the current gauge

frontend/apps/reader/modules/readerfooter.lua

@@ -52,7 +52,7 @@ local symbol_prefix = {
     icons = {
         time = "⌚",
         pages_left = "⇒",
-        battery = "",
+        battery = "",
         percentage = "⤠",
         book_time_to_read = "⏳",
         chapter_time_to_read = "⤻",
@@ -115,8 +115,10 @@ local footerTextGeneratorMap = {
                     prefix = ""
                 end
             end
+            return prefix .. batt_lvl .. "%"
+        else
+            return prefix .. " " .. (powerd:isCharging() and "+" or "") .. batt_lvl .. "%"
         end
-        return prefix .. (symbol_type == "icons" and "" or " ") .. batt_lvl .. "%"
     end,
     time = function(footer)
         local symbol_type = footer.settings.item_prefix or "icons"

spec/unit/readerfooter_spec.lua

@@ -217,7 +217,7 @@ describe("Readerfooter module", function()
         assert.are.same('0%', footer.footer_text.text)
 
         -- disable battery, percentage should follow
-        tapFooterMenu(fake_menu, "Battery status".." ()")
+        tapFooterMenu(fake_menu, "Battery status".." ()")
         assert.are.same('⤠ 50%', footer.footer_text.text)
 
         -- disable percentage, book time to read should follow